Kivy A to Z -- Kivy模块的加载
1. 如果你看下各模块下的生成的文件，你会发现so文件都是空的，如pyjnius,jnius.so就是空的
2. 这就奇了怪了，根据我们的知识储备，如果是调用了import jnius，并且jnius不是一个py,pyo或者pyc文件的话，那么python就会从动态库里去找initjnius进行模块的初始化了。
3. 但是现在动态库是空了，这是什么情况？
4. 还记得distribute.sh里的run_biglink吗？
5. 该函数把所有模块的o文件链接到libpymodules.so中
6. 但是python是怎么从里面取出相应的模块进行初始化的呢？
7. 答案在recipes\python\patches\custom-loader.patch里
8. 这是一个对dynload_shlib.c的patch，patch完后，dynload_shlib.c的_PyImport_GetDynLoadFunc就变成：
dl_funcptr _PyImport_GetDynLoadFunc(const char *fqname, const char *shortname,
const char *pathname, FILE *fp)
{
dl_funcptr p;
void *handle;
char funcname[258];
char pathbuf[260];
int dlopenflags=0;
static void *libpymodules = NULL;
void *rv = NULL;
/* Ensure we have access to libpymodules. */
if (libpymodules == NULL) {
printf("ANDROID_PRIVATE = %s\n", getenv("ANDROID_PRIVATE"));
PyOS_snprintf(pathbuf, sizeof(pathbuf), "%s/libpymodules.so", getenv("ANDROID_PRIVATE"));
libpymodules = dlopen(pathbuf, RTLD_NOW);
if (libpymodules == NULL) {
//abort();
}
}
if (strchr(pathname, '/') == NULL) {
/* Prefix bare filename with "./" */
PyOS_snprintf(pathbuf, sizeof(pathbuf), "./%-.255s", pathname);
pathname = pathbuf;
}
PyOS_snprintf(funcname, sizeof(funcname),
LEAD_UNDERSCORE "init%.200s", shortname);
/* Read symbols that have been linked into the main binary. */
if (libpymodules) {
rv = dlsym(libpymodules, funcname);
if (rv != NULL) {
return rv;
}
}
if (fp != NULL) {
int i;
struct stat statb;
fstat(fileno(fp), &statb);
for (i = 0; i < nhandles; i++) {
if (statb.st_dev == handles[i].dev &&
statb.st_ino == handles[i].ino) {
p = (dl_funcptr) dlsym(handles[i].handle,
funcname);
return p;
}
}
if (nhandles < 128) {
handles[nhandles].dev = statb.st_dev;
#ifdef __VMS
handles[nhandles].ino[0] = statb.st_ino[0];
handles[nhandles].ino[1] = statb.st_ino[1];
handles[nhandles].ino[2] = statb.st_ino[2];
#else
handles[nhandles].ino = statb.st_ino;
#endif
}
}
#if !(defined(PYOS_OS2) && defined(PYCC_GCC))
dlopenflags = PyThreadState_GET()->interp->dlopenflags;
#endif
if (Py_VerboseFlag)
PySys_WriteStderr("dlopen(\"%s\", %x);\n", pathname,
dlopenflags);
#ifdef __VMS
/* VMS currently don't allow a pathname, use a logical name instead */
/* Concatenate 'python_module_' and shortname */
/* so "import vms.bar" will use the logical python_module_bar */
/* As C module use only one name space this is probably not a */
/* important limitation */
PyOS_snprintf(pathbuf, sizeof(pathbuf), "python_module_%-.200s",
shortname);
pathname = pathbuf;
#endif
handle = dlopen(pathname, dlopenflags);
if (handle == NULL) {
const char *error = dlerror();
if (error == NULL)
error = "unknown dlopen() error";
PyErr_SetString(PyExc_ImportError, error);
return NULL;
}
if (fp != NULL && nhandles < 128)
handles[nhandles++].handle = handle;
p = (dl_funcptr) dlsym(handle, funcname);
return p;
}
9. 该函数会加载libpymodules.so
10. 并且会先判断initxxx是否在libpymodules里存在
11. 如果存在，则会返加该函数的指针
12. 好，又消除了心中的一个大疑问！
（完）